Nowadays, distributed power supply systems provided in areas near regions consuming electric powers are increased. The distributed power supply systems are a power generation system from a renewable energy resource such as solar power or wind power and a gas turbine power generation system, etc.
The gas turbine power generation system has a small size and it is operated in high efficiency. A related prior art is disclosed by WO2014/020772A1 (Patent Literature 1). The Patent Literature 1 describes that a dual-shaft gas turbine power generation system includes an electric motor connected to a shaft of a compressor and a frequency converter, which drives the motor, connected between the motor and a synchronous power generator connected to a shaft of a low pressure turbine. An air-flow to a burner is controlled by a rotation of the compressor assisted by the motor for variation in an outside air temperature. Consequently, the gas turbine is continuously operated in high efficiency without reducing fuel burned in the burner.
The distributed power supply systems connected to a power system supply their surplus power to the power system. As an electricity generation from the distributed power supply systems has variable nature, the distributed power supply systems connected to the power system cause a power fluctuation such as power oscillation in the power system. Particularly, a recent increase of the power generation systems from the renewable energy resources results a large power fluctuation. Thus, a function to stabilize the power system is necessary for the distributed power supply systems connected to the power system.
Stability of the power system can be improved by use of a Power System Stabilizer (PSS) which adjusts a setting value of an Automatic Voltage Regulator (AVR) in generator in order to damp power oscillation or power perturbation. A prior art in this technical field is disclosed by US2013/0234680A1 (Patent Literature 2). The Patent Literature 2 describes that a method of damping power oscillation in the power system includes generating synchronized generator speed signals by time stamping a plurality of generator speed signals. The synchronized speed signals are transmitted to a control station for determining the power oscillation in the power system. The control station provides damping control signals to a plurality of damping devices based on the power oscillation in the power system.